No abstract

Purpose The purpose of this paper is to investigate the impact of semi-circular zigzag-channel printed circuit heat exchanger (PCHE) design parameters on heat transfer and pressure drop of flows under high Reynolds numbers and provide new thermal-hydraulic correlations relevant to conditions encountered in natural gas processing plants. Design/methodology/approach The correlations were developed using three-dimensional steady-state computational fluid dynamics simulations with varying semicircular channel diameter (from 1 to 5 mm), zigzag angle (from 15° to 45°) and Reynolds number (from 40,000 to 100,000). The simulation results were validated by comparison with experimental results and existing correlations. Findings The results revealed that the thermal-hydraulic performance was mostly affected by the zigzag angle, followed by the ratio of the zigzag channel length to the hydraulic diameter. Overall, smaller zigzag angles favored heat transfer intensification while keeping reasonably low pressure drops. Originality/value This study is, to date, the only one providing thermal-hydraulic correlations for PCHEs with zigzag channels under high Reynolds numbers. Besides, the broad range of parameters considered makes the proposed correlations valuable PCHE design tools.

The aim of the current study is to characterize key multidimensional relationships between coherent structures in physical vs Fourier/scale space representations of flame–turbulence interactions, as a basis for future analysis of the nonlinear couplings between key resolved scale (RS) and subfilter scale (SFS) motions in large-eddy simulation (LES) of premixed turbulent combustion. However, applying the bounded Fourier transform (FTF) in the nonperiodic flame-normal direction requires the removal of nonphysical Fourier content from the boundary discontinuities. To this end, we have developed a broadly applicable “discontinuity pollution removal” procedure for application to the FTF of multidimensional signals with a single nonperiodic direction. The procedure balances periodization of the signal near the boundaries with minimization of signal modification away from the boundaries. We applied the procedure in a physical–Fourier space analysis of the interactions between a flame and single-scale eddies modeled as the impact of a train of two-dimensional (2D) vortices on an initially planar premixed flame. We find that a specific spectrally broad localized coherent structure in Fourier space connects RS to SFS fluctuations in thermal energy and species concentration that, in physical space, are localized to the corrugations in the flame front in response to eddy–flame interactions. Within the RS fluctuations of energy and species concentration, the flame corrugation structure in physical space is found to be localized to sub-volumes within the RS region of 2D Fourier space. This new understanding of physical–Fourier space relationships categorizes classes of RS–SFS interactions relevant to SFS modeling in LES of premixed turbulent combustion.

<div class="section abstract"><div class="htmlview paragraph">The development of efficient, reliable, and affordable Hybrid and Electric Vehicles (xEVs) relies on optimized Vehicle Thermal Management System (VTMS) architecture and control strategies. Compared to conventional vehicles, xEVs have more complex VTMS due to additional powertrain components and cooling circuits to meet distinct thermal requirements. The cooling circuits comprise a combination of hoses, straight, and bent pipes to route coolant flow around obstacles between powertrain components at distinct locations in the vehicle. The increased length and geometrical complexity of these piping systems, compared to conventional vehicles, results in increased pressure losses. Thus, accurate predictions of pressure drop within these piping systems is critical for component selection for an optimized VTMS. Numerical simulations are often used to study interactions between components from a system-level perspective allowing early stage rapid assessment of performance. In this work, an accurate 1D model for pressure drop in piping systems is developed based on literature review and validated using 3D Computational Fluid Dynamics (CFD) predictions. The 1D model is implemented in the software tool GT-SUITE which is used for integrated 0D/1D/3D multi-physics system simulation of the entire VTMS. The CFD calculations are performed using GT-CONVERGE. Overall, the pressure drop predictions of the 1D model are in good agreement with the 3D CFD for a range of Reynolds numbers including laminar, transition, and turbulent regimes and even when significant losses are present due to flow redevelopment after bends. Typically, commercial tools often ignore flow redevelopment and were originally developed for high Reynolds number flows. A typical battery electric vehicle is constructed in GT-SUITE and results indicate that deviations on pressure drop predictions lead to significant deviations on pump operating conditions and isentropic efficiency. The 1D model allows fast and accurate simulations over a broad range of complex piping configurations for an optimized VTMS.</div></div>

No abstract